Neutron-induced fission: properties of prompt neutron and γ-rays as a function of incident energy

We have applied the Hauser-Feshbach statistical theory, in a Monte-Carlo implementation, to the de-excitation of fission fragments, obtaining a reasonable description of the characteristics of neutrons and gamma rays emitted before beta decays toward stability. Originally implemented for the spontaneous fission of ²⁵²Cf and the neutron-induced fission of ²³⁵U and ²³⁹Pu at thermal neutron energy, in this contribution we discuss the extension of the formalism to incident neutron energies up to 20 MeV. For the emission of pre-fission neutrons, at incident energies beyond second-chance fission, we take into account both the pre-equilibrium and statistical pre-fission components. Phenomenological parameterizations of mass, charge and total kinetic energy (TKE) yields are used to obtain the initial conditions for the fission fragments that subsequently decay via neutron and γ emissions. We illustrate this approach for ²³⁹Pu(n,f). (authors)